1. Field of the Invention
The present invention relates to an ultrasound sensor for distance recognition for use in vehicles, and in particular to an ultrasound sensor having integrated blockage detection.
2. Description of Related Art
For driver assistance systems, in the area of motor vehicle technology ultrasound-based sensors are used that make use of a pulse-echo method to detect the object, or the environment surrounding the vehicle, on the basis of the reflected ultrasound pulse.
Because the associated ultrasound transducer is necessarily situated on the outside of the vehicle, problem situations occur as a result of weather conditions. If the externally situated transducer is covered by ice, snow, or other solid materials, no echo signal is detected, and the evaluation concludes that the surrounding space is free of objects.
In driver assistance systems that do not provide active support, this can cause accidents if the driver of the vehicle relies on this information. Driver assistance systems that provide active support determine the direction of travel and, if warranted, the speed of travel by themselves, so that a false estimation based on the above-named sensor errors can have serious consequences. The use of such sensor systems in, particularly, driver assistance systems providing active support therefore requires a high degree of reliability.
A sensor test involving active triggering before the beginning of travel is not practicable for a number of reasons.
Standard sensors known from the prior art do not guarantee this reliability, because in the presence of blockages, for example by slush, such sensors will not recognize an ultrasound pulse reflected by an object, and will also falsely assume that an ultrasound pulse was radiated even though the blockage means that only a small part of the energy, if any, was radiated to the surrounding environment.
An object of the present invention is therefore to provide an ultrasound sensor and a method by which the reliability of the sensors is significantly increased, in particular by recognizing such a blockage or blindness of the sensor.